ฉันรักการแปลThe major GA3ox of Arabidopsis (AtGA3ox1) is highly regiospecific, producing a single product, while enzymes from certain other species also oxidize neighboring C atoms to a small extent (26). For example, oxidation of both C-2 and C-3 produces a 2, 3-double bond, as in the conversion of GA20 to GA5. Further oxidation of GA5, initially on C-1 and then on C-3, by the same enzyme results in the formation of GA3 (2, 66). While most GA 3oxidases are specific for C19-GAs, some plants, and particularly seeds, produce 3ȕ-hydroxylated C20-GAs. For example, an enzyme from pumpkin endosperm 3ȕ-hydroxylates C20-GAs more readily than C19-GAs (41).
A third class of dioxygenase, GA 2-oxidase (GA2ox), is responsible for the irreversible deactivation of GAs by 2ȕ-hydroxylation, so ensuring GA turnover, which is necessary for effective regulation of GA concentration. In some tissues, such as the cotyledons and, particularly, the testae of